196 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



interior space. All the cells of the frond, except the lowest, 

 capable of producing zoospores or gametes, which are dis- 

 charged through an opening in the cell wall. 



A large genus, connected with Ulva by E. linza, in which 

 the tube is compressed, and the membranes united in the 

 median part ; on the other hand, Monostroma grocnlandicum is 

 hardly to be distinguished from some of the simple filiform 

 species of Enteromorpha. E. intestinalis is found the whole 

 world over, and other species are very widely distributed. They 

 are found not only in the sea, but about salt springs and salt 

 mines ; they abound in brackish water, and are occasionally 

 found in quite fresh water. 



At places wht^ the salinity of the water is subject to much 

 change, very perplexing forms occur ; specimens collected near 

 the salt mines at Syracuse, N. Y., show in the same frond char- 

 acters of E. compressa, E, crinita, and E. marginata. It is impos- 

 sible to say what is the normal form ; the specimens must be 

 considered as teratological. Specimens from Great Salt L/ake, 

 Utah, also show abnormal forms. 



KEY TO THE SPECIES OF ENTEROMORPHA. 

 i. Frond flat, the membranes free at the margins, but united between. 



19. E, linza. 



i. Frond of one to a few series of cells, not tubular. 2. 



i. Frond tubular. 3. 



2. Frond simple. i. E.percursa. 



2. Frond branched. 2. E. cruciata. 



3. Cells not arranged in longitudinal series except in the very youngest 



parts. 4. 



3. Cells more or less in longitudinal series, usually in the greater part 



of the frond. 9. 



4. Cells of the new generation in twos, threes and fours, in the wall 



of the mother cell. 16. E. fascia. 



4. Mother cell wall not persisting after division. 5. 



5. Frond with short, spine-like ramuli, in addition to branches. 



8. E. acanthophora. 



5. Frond with more or less plentiful branches. 6. 



5. Frond simple or with a few proliferations. 7. 



6. Frond with flattened rachis branching from the margin. 



17. E. micrococca var. subsaha. 



6. Frond filiform ; branches with contracted base, expanding upwards. 



10. E. compressa. 



